Chilmark gardener jump-starts her beds with cardboard

The ground is frozen solid in February, but Rebecca Gilbert says that it’s the perfect time to lay out new garden beds. She teaches a workshop about how to use cardboard as mulch, which she promotes as an easy, organic, and elegant way to break ground for a new garden. Ms. Gilbert says that this method is best for small gardens, and it’s a great way for people to grow food in small patches everywhere, without backbreaking labor.

Ms. Gilbert’s grandparents bought the property on North Road in Chilmark where she farms in the 1920s. “My grandmother was a big gardener,” she said, “so all my childhood, as a summer kid, I gardened with her. Some of my earliest childhood memories were of sitting in my grandmother’s garden and tasting things.”

Ms. Gilbert opened Native Earth Teaching Farm to the public in 2002. The farm has community gardens, pigs, goats, and a wide variety of poultry. “It’s very important to give kids early memories of gardening,” she said, “and that’s why we have so many community gardens and encourage people to have gardens in their own yards, even if they’re small. Cardboard mulch is just a great method to put a little garden in your yard.”

The first step is to decide where to put the garden. Ms. Gilbert places sheets of cardboard on the ground where she thinks she might like to put the garden. This helps her visualize what it will look like in the yard.

Once a spot is chosen, the method basically consists of laying the cardboard on the ground and leaving it there for several months, weighed down with compost, logs, stones, or anything that will keep the cardboard from blowing away. The fertility of the soil is enhanced by layering lime and organic compost underneath the cardboard. Ms. Gilbert provides a tour of her compost piles as part of the workshop.

Once the cardboard is in place, the gardener’s job is to step aside and let the soil organisms do their work. Once it gets wet, the cardboard sticks to the soil, becomes soft and porous, and lets moisture through while blocking light. This stops weeds from growing and allows earthworms and light-sensitive microorganisms to come up closer to the surface than they would in an un-mulched patch of soil.

“For every worm there are many microscopic organisms doing the same thing on a microscopic scale,” says Ms. Gilbert. “The more diverse that community, the more flavor your food plants will have.”

Ms. Gilbert says that the glues in cardboard and the black and brown inks in newsprint are mostly benign and don’t add toxins to the soil. Colored inks and shiny paper contain more heavy metals.

“Toxins in colored ink vary a lot,” she says. “There are some heavy metals in some colored inks that could theoretically build up in the soil, but you don’t have to be fanatical about it. The soil organisms can process quite a bit, but we’re trying to make it easier for them, not harder.”

After a few months, when the ground has thawed and mud season has passed, it’s time to plant. By this time, the soil beneath the cardboard should be nice and fluffy, and all the gardener has to do is poke through the mulch and gently plant into the soil below. It’s important not to walk on the beds, which would compact the soil. The mulch stays in place as the garden grows, continuing to suppress weeds through the growing season.

Although this method could be used on larger areas, Ms. Gilbert says, “It’s best for places where you don’t want to bring in a tractor, like putting a tree in the middle of your lawn, or for planting right next to the house.” She has used this method for planting trees and for laying out a circular herb garden in front of her house. The technique allowed her to expand the garden gradually and to see its design in place as she went along.

Ms. Gilbert plans to offer this workshop again in March, and says that she will run a small class whenever two or three people are interested in learning one of these techniques. Information about this and Ms. Gilbert’s other classes and workshops is available at nativeearthteachingfarm.org.